Answer:
The side lengths are 5, 12, 13
Step-by-step explanation:
These are the side lengths we know before we have solved the problem.
a= x b= x+7 c= 13
If we put this into the Pythagorean theorem, we get

Expand

Subtract 169 from both sides

Solve using the quadratic formula
a= 2 b= 14 c= -120

If we separate the solutions we get

and
Since this is a question about length, we can ignore the negative.
So the longer leg is 12ft and the shorter leg is 5ft